Method of making filter elements



June 15, 1937. Q Q RENSlNK 2,983,865

METHOD OF MAKING. FILTER ELEMENTS Original Filed July 22, 1935 Inventoreavge U. Wendi wk.

- flttorney' Patented June 15, 1937 UNITED STATES PATENT OFFICE 32,549.Divided and this application September 21, 1936, Serial No. 101,814

3 Claims.

This invention relates to improvements in filter elements and methods ofmaking the same.

In air cleaners and other apparatus for filtering air and other gases itis necessary to employ a fibrous filter that is very weak and which mustbe reenforced by means of woven wire cloth such as is ordinarily usedfor sieves and screens. The filter cloth or material is composed ofmatted fibers formed into thin layers and may be likened to very thinand loose felt and in its normal state it is very diflicult to handlewithout tearing. It is the object of this invention to produce a methodof treating the filter material so as to give it added. strength toresist tearing while I it is handled and which can be restored to its;original state by lixiviation. In order to describe the invention sothat it can be readily understood and practiced by any one skilled inthe art, reference will now be had to the accompanying drawing in whicha section of filter has been shown and in which, Fig. 1 is a plan viewshowing a section of filter made in accordance with my invention;

Fig. 2 is a section taken online 2-2 Fig. 1;

I and Fig. '3 is an end view of a cylindrical filter assembly.

The filter which forms the subject of this invention consists of twoparallel layers of woven wire screen that have been designated bynumeral 2. Located between the screens is a sheet of filter material 3of the kind referred toabove.

Before the filter cloth or material is put in place, it is saturatedwith a strong solution of salt or sugar, spread on a fiat surface'andleft until it has become dry. The solution is preferably a strong or asaturated one and the salt or sugar orother equivalent soluble materialcrystallizes on the fibers of the-filter material and the latter becomeshard and stiff so that it can be safely handled. 4 The treated fibrousfilter material-is now out to the desired size and shape and placedbetweenthe screen sections and the latter are assembled into the desiredshape; In Fig. 3 a section of a cylindrical or a frusto-conical screenhas been shown as this is the form that is usually employed in aircleaners.

50 -After the filter has been assembled, the entire assembly is immersedin water and, the salt,

sugar or other soluble material used is dissolved and by washing thefilter thoroughly is completely removed and therefore after the filterhas 55 dried the filter cloth'will be in its original condition.

By the simple method just described any delicate fibrous material can beput in such a condit on that it can be safely handled and can be re- 60stored to its original condition by washing thor- (Cl. lax-'44) oughlywith clean water until the salt or sugar has been entirely removed.

In the above description salt has been used in its broad sense and isnot limited to sodium chloride as there are many other soluble saltsthat 5 can be used as, for example, Epsomsalt.

When the filter cloth, which is preferably not a cloth in the sense thatit is woven, is treated as described above, it becomes hard and strongand can be handled without danger of tearing. 10

The treated filter material 3 is clamped in place between sheets ofscreen and is protected by the latter and in this way it is possible toemploy very delicate and efiicient filter material and still run noappreciable risk of having it tear 15 when in use. I

A filter screen made in accordance with this invention has acomparatively smooth outer surface which prevents dust from adhering andthe filter therefore does not clog with dust be- 20 cause the vibrationsto which it is subjected when used on an automobile keeps its outersurface clean.

This application is a division of my copending application Serial Number32,549 filed by me 25 on July 22, 1935 which is now Patent No.2,067,160, granted Jan. 5, 1937.

Having described the invention what I claim as new is.

1. The method of treating a 'sheet of delicate fibrous filter materialto facilitate handling and forrestoring it to its original condition,which comprises, saturating the sheet with a strong solution of asolublecrystalline compound, evaporating' the liquid, whereby thecompound will 35 crystallize on the fibers, and after the fibrousmaterial has been subjected to the required handling, removing thesoluble compound by lixiviation,

2. The method' of forming a filter elementiconsisting of a thin sheet offibrous filter material positioned between two or more sheets of wovenwire, which comprises saturating the sheet with a strong solution of asoluble crystalline conipound, evaporating the liquid, whereby theresidue from the evaporation will be deposited on I the fibers,assembling the filter element; and renaiving the soluble crystallinematerial by lixivia on.

3. The method of forming a filter element consisting of a thin sheet offibrous filter material positioned between two sheets of woven wire,which comprises saturating the sheet. with a strong solution of asoluble crystalline compound, evaporating the liquid, whereby thesoluble compound will be deposited on the fibers, compacting the fibrousmaterial between the sheets of woven wire, and thereafter removing thecrystalline compound by lixiviation.

' GEORGE C. REN SINK. 6i)

